Like a virus, revolt has spread rapidly over the last few weeks from Tunisia to Egypt, with additional riots and protests in nearby Jordan and Yemen and rumblings that Syria may be next.

As alarming as the spread of uprisings might be, the recent chain of events echoes numerous periods of discontent that stretch back more than 200 years.

From a series of revolutions that swept Europe in 1848 to the impact of the Berlin Wall's demise in 1989, unrest has triggered more unrest, time and again — especially since the advent of mass communication allowed word to spread quickly from one place to another.

"Revolutions can sometimes be contagious," said John McManus, a military historian at Missouri University of Science and Technology in Rolla. "The take-home lesson from history is that you always have no idea how it's going to turn out, and that's kind of the scary part. You have no idea where the forces are going to go once they're unleashed."

Perhaps the earliest historical example was the American Revolution against Great Britain. Its success in 1776, in the view of most historians, inspired France to seek and win its own independence by 1789.

A more extensive spread of strife began in France in 1848, when disenfranchised members of the lower middle class revolted against King Louis Philippe's corrupt and elitist rule. As Louis Philippe fled the country, rebellion spread to Germany, where people already held similar grievances and the idea of rebellion had been long fermenting. From there, revolt surged through Austria, Poland, Russia, Italy and beyond.

"There's no question that one thing leads to another," McManus said. "People see it going on in France. They see that, yeah, it can be done, and maybe the time is right. Revolution literally spread like wildfire that year."

Other examples include the secession of South Carolina in 1860 from what the state saw as a tyrannical American government. Alabama, Mississippi and other Southern states followed, a domino effect that led directly to the Civil War. And the fall of the Berlin Wall in 1989 was part of a wave of uprisings against Communism in Poland, Romania, Hungary, Czechoslovakia and Bulgaria.

While the current situation in the Middle East involves its own unique cultural and political details, it shares many common themes with the past, said Ziad Fahmy, a historian of modern Egypt at Cornell University in Ithaca, N.Y.

Like other contagious revolutions, he said, this one began years ago with a stewing sense of dissatisfaction toward an oppressive regime, along with growing urban centers and other deeply rooted cultural changes. Such unhappiness often sets the stage for a trigger event, which begins the toppling of metaphorical dominoes.

In this case, the trigger was a Tunisian protester who set himself on fire in mid-December. Subsequent protests led quickly to the flight of Tunisia's president and similar revolts in neighboring nations.

For a single revolt to become contagious, Fahmy added, communication is key. In 1848, it was the recently invented telegraph, along with printed newspapers, that clued people in to what was happening across national lines.

Today, it's Facebook, YouTube and Twitter. And when electronic means failed, Egyptian protesters made do the old-fashioned way, with printed instructions about what to do.

At its heart, rebellious contagion feeds off of the sense of inspiration people feel when they see people in similar situations striking back — and succeeding.

"People see that as a template that they can follow, and they see that it can happen," Fahmy said. "It begins to chip away at that barrier of fear."

What history can't do is help experts predict where revolutions will begin, how far they will spread or how it will all end. Outcomes are often surprising and not always positive. Looking to the past, Fahmy said, is also unlikely to prevent new revolts from cropping up in the future and spreading like the flu.

"No one ever learns from history," he said. "There are always going to be new grievances and new media. This is human nature. When people are oppressed, they will revolt."